多视场宽时域仿生极高速成像

Bionic Ultrafast Imaging for Multi-FOV and Wide Time Range

现有极高速成像系统存在元件复杂、系统庞大以及视场受限的问题。基于螳螂虾小眼和复眼结构提出一种结构紧凑的极高速成像方法,可应用于多种视场和时间范围。仿生极高速成像仿生微绒毛阵列结构,以条纹结构光照明和空间角分复用为基础,实现图像的压缩和瞬态事件时序图像的重现。仿生螳螂虾小眼结构,可以实现视场极高速成像;而复眼系统结构上有小眼系统拼接组成,可以突破限制现大视场极高速成像。时间延迟结构与照明成像光路分离,可以实现飞秒至皮秒时间尺度的瞬态事件记录。因此,仿生多视场极高速成像理论上可以应用于各种视场的成像,仿真实验的摄影频率可以达到1.2×10^(13)帧/s,还原图像分辨率可以达到80.6 lp/mm。仿生极高速成像为大范围、群体性瞬态事件的探测提供了可能,例如光在散射介质中的传播、随机运动等,并且其结构紧凑,为极高速成像仪器的小型化、轻量化打下基础。

The existing ultrafast imaging systems can record dynamic events on the femtosecond time scale,but they have the problems of complex components,large systems,limited field of view and time range.The single-shot ultrafast imaging technologies by direct imaging can realize the recording of dynamic images through spatial separation of temporal images.However,their detection systems have the problem of complex structures.The ultrafast imaging system combined with algorithms simplifies the detection structure,but there are some problems,such as complex framing system,limited time range and field of view.This paper proposes a single-shot ultrafast imaging method inspired by the eyes of mantis shrimp,which can be applied to multiple fields of view and wide time range with a compact structure.In this bionic system,the structure light illumination principle is inspired by the orthogonal microvillus arrays,the ommatidium system optical path leads to the optical path of mantis shrimps’ommatidium,and the optical path of compound system is inspired by the compound eye of mantis shrimp,which expands the field of view.Single-shot bionic ultrafast imaging uses a step reflection array to generate sequential pulses of different frequencies and directions and interference fringe structured light illumination to divide the sequential images.It realizes images compressed in a single detector and reconstruction of the continuous images based on the spatial angle division multiplexing algorithm.The bionic mantis shrimp structure can realize single-shot ultrafast imaging,while the compound eye structure is composed of ommatidium systems splice,which can break through the limit size of the field of view to achieve a large field of view.The feasibility of interference fringe multiplexing is verified by static test,and Zemax establishes an optical model to realize the sequential image restoration of ommatidium and compound eye system of 8 images.The framing time is discussed and verified.FDTD simulation is used to verify the feasibility of generating sequential pulses by the step array of mirrors.The framing time can be changed by adjusting the height of adjacent steps,and achieving framing times of 78 fs and 1 ps,and the sequential pulses are not widened compared with the incident pulses.By analyzing the factors affecting the framing time of the bionic singleshot ultrafast imaging system,it can be concluded that the framing time mainly depends on the width of the sequential pulses,so its photographic frequency can reach 10^(13) frame/s.Besides,the time delay structure and imaging structure are independent.Dispersion element and narrowband filter array can be used instead of mirror arrays to realize time delay.As the dispersion elements can be glass columns,prism pairs,grating pairs,and optical fibers,the bionic system can expand femtosecond pulses to hundreds of femtosecond,picosecond,or nanosecond time scales.Hence the bionic ultrafast imaging system enables the recording of dynamic events on femtosecond,picosecond,or nanosecond time scales.The influence factors of the spatial resolution are then further analyzed.The optical system can achieve high spatial resolution,which can reach the pixel scale of the detector.Furthermore,it can also obtain high-quality restored images,and its intrinsic spatial resolution can theoretically reach 80.6 lp/mm.The bionic system can be used to detect various fields of view by adjusting the focal length of each lens.Hence,it can cover various fields of view.In conclusion,single-shot bionic ultrafast imaging can be applied to various sizes of the field of view in theory,and the framing rate can reach 1.2×10^(13)frame/s in simulation experiment.Single-shot bionic ultrafast imaging provides the possibility for detecting a large range of transient group events,such as light propagation in the scattering media,random motion.Its compact structure lays a foundation for miniaturization and lightweight of ultrafast imaging instruments.